/* expand_mask.c -  convert bitmas to a byte mask */

#include <stdio.h>
#include <math.h>

unsigned char maskset[8] = { 128, 64, 32, 16, 8, 4, 2, 1};

main(argc, argv)
int	argc;
char	**argv;
{
	FILE	*fpi, *fpo;
	int	i, ntot, nmask;
        unsigned char *a, *b;

/* read the command line */

        if (argc != 4) {
                fprintf(stderr,"usage:  expand_mask <input.bit > <output.byte> ntot\n");
                if (argc > 1) fprintf(stderr,"expand_mask:  ERROR.  Cannot open r %s\n", argv[1]);
                exit(-1);
        }

        if ( (fpi = fopen(argv[1], "r")) == NULL) {
                fprintf(stderr,"expand_mask:  ERROR.  Cannot open r %s\n", argv[1]);
                exit(-1);
        }

        if ( (fpo = fopen(argv[2], "w")) == NULL) {
                fprintf(stderr,"expand_mask:  ERROR.  Cannot open w %s\n", argv[2]);
                exit(-1);
        }
        ntot=atoi(argv[3]);
        nmask=ntot/8;

/*  allocate memory */

        if(( a = (unsigned char *) malloc(nmask)) == NULL){
                printf("sorry, couldn't allocate memory for mask\n");
                exit(-1);
        }

        if(( b = (unsigned char *) malloc(ntot)) == NULL){
                printf("sorry, couldn't allocate memory for bytemask\n");
                exit(-1);
        }

/*  read the bit mask */

	if ((fread(a, 1, nmask, fpi)) != nmask) {
		fprintf(stderr,"expand_mask:  ERROR during read of %s\n", argv[1]);
		exit(-1);
	}
	fclose(fpi);

/*  convert bits to bytes */

	for (i = 0; i < ntot; i++) {
          b[i] = 0;
          if((a[i/8] & maskset[i%8]) > 0) b[i] = 1;
        }

/*  write the byte mask */

	if ((fwrite(b, 1, ntot, fpo)) != ntot) {
		fprintf(stderr,"expand_mask:  ERROR during write of %s\n", argv[2]);
		exit(-1);
	}
	fclose(fpo);

	exit(0);
}